Please follow my deduction and tell me where am I wrong, or maybe I’m not? 1) the cosmological principle: "Viewed on sufficiently large distance scales, there are no preferred directions or preferred places in the Universe" it says that there is no center of the universe, or in other words – the centre is everywhere, like on a sphere, balloon, circle etc. 2) the Hubble law: "The galaxies are all receding from us if we go to large enough distances; the velocity of recession is proportional to the distance from us." That means that the expansion of the universe, viewed form everywhere, is like blowing the balloon up. And the SURFACE of this balloon is 3D! If the universe is a 3D surface of a sphere so the sphere should be a 4D hypersphere i.e. a sphere of 4 SPATIAL dimensions? S.